[OpenTRV-interest] First impressions and questions

[Damon Hart-Davis]

> On 26 Jan 2017, at 07:51, Simon Hobson <linux at thehobsons.co.uk> wrote:
> 
> Another thought, one for Damon ...
> 
> A back in October I asked about two rads in one room (the thread is titled "Multiple rads in one room"), and would the TRVs "fight". There was a comment from Damon :
> 
> 
> On 8 Oct 2016, at 20:54, Damon Hart-Davis <dhd at exnet.com> wrote:
> 
>> Nominally we can slave a second radiator from another one, but we haven’t tried/implemented it yet.  Should not be too hard to put together a config that supports it, and we could help you create such a config.
>> 
>> We have tested OpenTRV controlling two rads in one room independently; seems OK but could probably be improved.
> 
> I would imagine that similar considerations apply there as to using a remote sensor, so it may be useful if the Radbot guys could outline what they had in mind and perhaps someone with enough interest/time/skill could take a look and see how it might be implemented.

Spoke today to two current split-unit OpenTRV trialists, with whom this has come up before.  Both have found solutions effectively passively slaving one rad to the other, with or without OpenTRV on the second.  

I’d be concerned that attempting to drive them as one would simply show up other imbalances eg between the open points, flow rates, etc.

But it is certainly possible and should be fairly simple to test code for if anyone wants to try.

One way, for example, might be to take a TRV1.5 valve and drop in a FHT8V control module driven as a slave and in parallel with the direct motor drive to control a second rad.  The FHT8V driver can TX on a separate channel from the new secure one quite easily in principle (there is explicit support for this).

That might be quite interesting to one or both of the above trialists.

Rgds

Damon